Device and method for fixing a toner image using a directed stream of solvent vapor

ABSTRACT

In a vapor fixing device for an electrographic printer or copier, the heated vapor housing is provided such that vapor does not condense at the interior housing walls. A directed stream containing solvent vapor is produced which is directed at a section of the support material.

BACKGROUND OF THE INVENTION

The invention is directed to a device and to a method for fixing a tonerimage on a carrier material, whereby the toner image is charged with asolvent vapor. The invention is also directed to an apparatus forprinting and/or copying wherein such a device is utilized.

In numerous electrophotographic printing or copying processes, a tonerimage is transferred onto a carrier material, for example paper, thetoner image being initially not joined to the carrier material insmear-proof and abrasion-resistant fashion. That the toner image isfirmly joined to the carrier material, i.e. fixed, is only achieved by afixing process. A fixing process is usually employed wherein the toneris charged with heat and pressure. The toner is thereby melted with theassistance of heating fixing drums and pressed into the carriermaterial, so that the toner enters into a bonded union with the carriermaterial. When no specific pre-heating of the paper is undertaken, thisheat-pressure fixing is limited to the transport velocity of the carriermaterial, for example to approximately 0.5 m/s through 0.7 m/s.

When the carrier material is simultaneously printed on both sides in theoperating mode of duplex printing and both sides are to besimultaneously fixed, then fixing drums that are soft and yielding mustbe employed at both sides. Such fixing drums have only a short servicelife and, due to the slight economic feasibility, are only utilized inprinters or copiers having a low printing volume. Due to the resilienceof the fixing drums, further, the guidance of the carrier material isproblematic, so that an endless carrier material web can only beconditionally employed given such a fixing method.

Contactless fixing methods have already been proposed that avoid theproblems arising due to the contact between carrier material and partsof the fixing mechanism, for example the fixing drums.

EP-A-0 629 930 discloses an arrangement wherein toner is melted withinfrared radiation and is fixed on the paper. Such an arrangement canalso be employed in duplex printing, whereby toner images aresimultaneously fixed on both sides of the carrier material. Whenswitched on and off, the infrared radiators that are employed have arelatively great time constant, so that a start/stop mode cannot berealized with such an arrangement without spoilage or rejects.

DE-A-198 27 210 discloses an arrangement wherein infrared radiation islikewise employed for fixing. A start/stop mode without rejects can berealized by means of the design control of a blind that is inserted intoand in turn withdrawn from the beam path of the infrared radiation.However, the general disadvantage of fixing with the assistance ofinfrared radiation remains, this being comprised such that the carriermaterial, generally paper, is relatively intensely dried during thefixing event, this leading to a shrinkage, to ripple and to anelectrostatic charging given further-processing and post-processing ofthe carrier material. Such a modification of the carrier material canlead to considerable problems in the post-processing of the carriermaterial, for example when cutting, stacking, binding, enveloping, etc.

Another known contactless fixing method is photoflash fixing wherein thetoner is fixed on the carrier material with high-energy light pulses.The wavelength of the radiation generally lies in the visible throughultraviolet range of the radiation spectrum. Photoflash fixing reactssensitively to the color of the toner, i.e. the toner material absorbsthe energy dependent on the existing light spectrum, which can lead toquality losses given employment of toners having different color, forexample in multi-color printing.

Another contactless fixing method is what is referred to as cold fixing.In this cold fixing, the toner material is softened under the influenceof a solvent. The softened toner thereby moistens the carrier material.Given employment of fiber material that contains fibers such as, forexample, paper or textiles, the softened toner surrounds the fibers and,due to capillary forces, penetrates between the fibers and into them.After the evaporation of the solvent, the toner in turn congeals andsolidifies. In this way, the toner is joined to the carrier material ina smear-proof and abrasion-resistant manner. The presence of the solventin vapor form during the fixing process is more advantageous than thepresence as an aerosol or liquid, since chemical solvent processessequence on a molecular basis and a molecular distribution of thesolvent is thus the most suitable. Given the employment of vapor,moreover, a condensation of the solvent vapor onto the toner particlesoccurs due to the different temperatures of carrier material and vapor,so that the vapor molecules deposit directly onto these toner particles.Moreover, the output of the evaporation enthalpy in the condensationsupports the softening of the toner and increases the speed of thedissolving process.

A general advantage of fixing with the assistance of a solvent is theslight thermal stressing of the carrier material. Accordingly, carriermaterials can be employed that withstand only a slight thermal ormechanical load such as, for example, labels or films. Moreover, themoisture content of the carrier material is not changed, so that aripple, a bagging or a curling arising due to changes in moisture areavoided. Moreover, cold fixing is largely independent of the thicknessof the carrier material, so that, for example, papers having differentpaper thicknesses can be employed without a great modification of thefixing process. In this way, a change in the type of paper can alsooccur with little expense.

U.S. Pat. No. 4,311,723 discloses an arrangement wherein a paper web isconducted through a fixing chamber with solvent vapor. The solvent vaporis situated in a container. Due to the force of gravity as well ascooling tubes in the upper region of the container, the concentration ofthe solvent vapor increases toward the floor of the container, so that aregion with a high solvent concentration arises in the proximity of thecontainer floor. The carrier material, which enters in the upper regionof the container with the as yet unfixed toner images, is deflecteddownward at a first deflection device and is conducted in the region ofthe high solvent concentration in the proximity of the container floor.The carrier material with partially fixed toner images is deflectedagain thereat at a second deflection device and is ultimately conductedupward out of the container via a third deflection device. Of necessity,a touching of the carrier material occurs at the deflection devices, asa result whereof the toner situated thereon can smear or peel off orprint locations are left behind. It is therefore not possible with thisarrangement to fix carrier material charged with toner images on bothsides. Moreover, the arrangement exhibits a relatively slow start/stopbehavior since—for stopping the fixing—the deflection device must bemoved out of the region of high solvent concentration upward into aregion having a low solvent concentration with which a fixing no longeroccurs, a certain time being required for this.

The employment of solvent can be problematical in view of the creationof ozone. One speaks of the ozone potential of a solvent in thiscontext. In U.S. Pat. No. 4,311,723, an azeotropic mixture oftri-chlorofluorethane (C₂Cl₂F₃, CFC1130 and acetone (C₆H₆O) is employed.The primary solvent is the acetone, whereas the CFC113 serves as a flameretardant. The use of CFC113 was outlawed in the earlier 1990s due tothe high ozone potential. Partially halogenated hydrocarbons, what arereferred to as HCFC, were then proposed as a replacement for the CFC113,for example HCFC123 and HCFC141b, since these have a significantly lowerozone potential. These partially halogenated hydrocarbons HCFChenceforth assumed the function of the flame retardant in mixtures ofair and combustible solvents such as acetone, propyl alcohols, etc. Inparticular, the use of pure HCFC141b without addition of a solvent suchas, for example, acetone proved advantageous given employment ofpolystyrol-based toners since HCFC141b has an adequate fixing action forthese toners and is simple to recover as a single-phase material sinceno mixing or de-mixing problems occur.

Due to its ozone potential and the environmental pollution produced as aresult thereof, however, HCFC141b will only be available for a limitedtime. New fixative mixtures on the basis of chlorine-free, fullyhalogenated hydrocarbons HFC were therefore proposed, for example inEP-A-0 784 238 (Solvay) and EP-A0 941 503 (Allied Signal). Given thepolyester based toners that are usually employed now, however, thesemixtures have proven problematic to employ in practice.

EP-A-0 613 572 discloses a method and a solvent for fixing a tonerconstructed on the basis of polystyrol. A partially halogenatedfluorohydrocarbon having a temperature of ebullition below 35° C. isemployed as sole a solvent.

DE-A-2 720 247 discloses a printing process wherein toner is transferredfrom an intermediate carrier, for example a photoconductor drum onto arecording medium at a transfer printing station. The toner on thephotoconductor drum is charged with a solvent vapor such that it becomessticky. The recording medium, for example the paper, is likewise exposedto the solvent vapor. The sticky toner adheres on the paper, which islikewise provided with solvent, as a result whereof the transferprinting event and the fixing of the toner occur in a single process.

DE-A-2 613 066 discloses a fixing process for fixing toner images onpaper. Hot gas with a predetermined proportion of water steam isemployed for the non-contacting fixing.

DE-A-2 613 066 also discloses a fixing device wherein the toner materialof the toner image on the recording medium is charged with a hot gas,particularly air. The temperature of this gas is such that the tonermelts and penetrates into the recording medium, for example paper.

The following documents are cited in the International Search Report:CH,A,457 144; U.S. Pat. No. 3,680,795; “Cut-Sheet Vapor Fuser”, IBMTechnical Disclosure Bulletin, IBM Corp. New York 32 (3A), 1989,258-259, XP000049471; DE,A,29 27 453; DE,A,36 36 324, with CH, A, 457144being relevant.

SUMMARY OF THE INVENTION

An object of the invention is to specify a device and a method thatenables a fixing of toner images with high efficiency given lowenvironmental pollution. This object is achieved by providing a methodand apparatus wherein a vapor fixing is provided such that vapor doesnot condense at interior housing walls.

Exemplary preferred embodiments of the invention are explained below onthe basis of the drawing, whereby known fixing mechanisms are alsoreferenced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a known fixing device with solvent vapor that is largely atrest;

FIG. 2 shows the structure of an inert air layer between the paper weband the solvent vapor;

FIG. 3 illustrates the effect of a solvent depletion;

FIG. 4 illustrates the principle of blowing the carrier material with adirected stream in a preferred exemplary embodiment;

FIG. 5 illustrates the schematic structure of a fixing device in apreferred exemplary embodiment;

FIG. 6 is a preferred exemplary embodiment wherein the carrier materialis blown from above and below;

FIG. 7 is an exemplary embodiment wherein the counter-current principleis realized;

FIG. 8 shows the generation of the directed stream by expansion of theevaporating solvent;

FIG. 9 is a simplified version according to FIG. 8;

FIG. 10 is an example with evaporator chambers that are arranged outsidethe fixing chamber;

FIG. 11 is an exemplary embodiment wherein the carrier material ischarged with a directed stream from only one side;

FIG. 12 is the example according to FIG. 11 but with the counter-currentprinciple realized therein;

FIG. 13 shows two series-connected fixing chambers;

FIG. 14 is the example according to FIG. 13, whereby the co-current flowprinciple is realized in one chamber and the counter-current principleis realized in the other chamber;

FIG. 15 shows two series-connected circulations with solvent vapor in asingle chamber;

FIG. 16 is an embodiment wherein the carrier material is verticallyconducted through the fixing chamber;

FIG. 17 is an exemplary embodiment wherein the carrier material isconducted through the fixing chamber at an angle of 45°;

FIG. 18 shows the exemplary embodiment according to FIG. 6, whereby thecontrol flaps are pivoted into the deflection position; and

FIG. 19 is an exemplary embodiment with further control elements.

DESCRIPTION OF THE PREFERRED EMBODIMENT

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to the preferred embodimentillustrated in the drawings and specific language will be used todescribe the same. It will nevertheless be understood that no limitationof the scope of the invention is thereby intended, such alterations andfurther modifications in the illustrated device, and/or method, and suchfurther applications of the principles of the invention as illustratedtherein being contemplated as would normally occur now or in the futureto one skilled in the art to which the invention relates.

FIG. 1 shows the structure of a traditional fixing device similar tothat according to the aforementioned U.S. Pat. No. 4,311,723. In orderto understand the exemplary preferred: embodiments of the inventionbetter, this known fixing device shall be discussed first. A solventvapor 12 is generated in a container 10. Cooling tubes 16 that cool thesolvent vapor are arranged inside the container 10. Accordingly, thesolvent concentration in the upper region 18 is lower than in a middleregion 20 and is in turn lower in the middle region 20 than in the floorregion 14. The highest solvent concentration is thus encountered on theportion 22 a of the web 22 in this floor region 14. The carrier material22, generally a paper web, with as yet unfixed toner images, entershorizontally into the container 10 and is deflected vertically downwardat a first deflection device 24 and is guided into the region of highsolvent concentration in the floor region 14. The toner images arepartially fixed over this path of the paper web 22. The paper web 22 isdeflected again at a second deflection device 26 and is ultimatelyconducted out of the container 10 via a third deflection device 28.

Of necessity, contact between the paper web 22 and the deflectionelements occur at the deflection devices 24, 26 and 28. Due to thiscontact, particularly at the elements 24 and 26, the toner can smear orcome off and/or print locations can remain behind on the paper web 22. Adouble-sided, simultaneous fixing of toner images on both sides of thepaper web 22, as would be necessary given the operating mode of duplexprinting, is not possible since the toner on the back side would alreadybe smeared at the first deflection device 24. Moreover, the still softtoner could in turn be partially stripped off at the third deflectiondevice 28.

The device shown in FIG. 1 also exhibits a relatively slow start/stopbehavior when the paper web 22 is arrested during forward transport orresumes its transport velocity. For stopping the fixing process, thedeflection device 26 is moved from the region with high solventconcentration, the floor region 14, upward into the upper region 18 withlow solvent concentration at which the fixing process is greatlyreduced. The travel motion consumes a relatively long time and thusdefines the dynamic behavior of the overall fixing device.

FIG. 2 schematically shows an effect that arises due to the motion ofthe carrier material 22. It must be generally mentioned that paper ispreferably employed as carrier material 22; however, other materialssuch as, for example, films, labels or plastics can also be employed.Given a movement of the paper web 22 in the direction of the arrow P1,air 30 is entrained from outside the fixing device. This air 30 islocated as an inert layer between the paper web 22 and the solvent vapor12, as a result whereof the fixing process is retarded since the solventvapor 12 must first penetrate the air layer 30. This effect is dependenton the transport velocity of the paper web 22 and on the spatialgeometry of the fixing device. This effect is especially pronounced whenthe solvent vapor 12 is at rest.

FIG. 3 shows a further effect that particularly occurs when the solventvapor 12 is at rest. The temperature of the paper web 22 generally liesbelow the temperature of ebullition of the solvent, so that the solventvapor 12 condenses at the surface of the paper web 22. A solventdepletion occurs in a zone 32 close to the surface of the paper web 22,so that the surface of the paper web is separated from the highlyconcentrated solvent vapor 12 and the toner cannot be dissolved anyfurther.

FIG. 4 shows the principle employed in the preferred embodiment. Thesurface of the carrier material, for example the paper web 22, is blownby a directed stream that contains solvent vapor 12. The stream 34emerges from a nozzle 36. The stream 34 of solvent vapor 12 penetratesthe inert air layer 30 and proceeds into a region 38 of the papersurface in order to dissolve the toner thereat.

The strong convection produced by the flow increases the probabilitythat solvent molecules encounter toner particles during the transit timeof the paper web 22 through the fixing device and dissolve the toner.The stream 34 is comprised of a mixture of air and solvent vapor. Thezone 32 with solvent depletion shown in FIG. 3 cannot form due to theconvection, since new solvent vapor 12 is continuously replenished. Ahigh solvent concentration is thus always maintained at the locationthat is blown against. The effect of this blowing principle is that anadequate dissolving effect is achieved even given a slight chemicaldissolving force and the required influencing time is shortened. Byshortening this influencing time, the structural size of the fixingdevice can be diminished with a given paper velocity, or the papervelocity can be increased with a given structural size.

FIG. 5 schematically shows the structure of a fixing device [of theinvention] for a simultaneous double-sided fixing of toner images on thecarrier material 22. The fixing device comprises a fixing chamber 40that has an essentially closed structure in order to prevent the activesolvent vapor from being diluted with ambient air. The carrier material22, generally a paper web, traverses the fixing chamber 40 straight andhorizontally, whereby it passes through a first, narrow admission gap 42and a narrow discharge gap 44 lying opposite the former. The admissiongap 42 is designed such that no contact occurs between it and thecarrier material 22 even when the web of material flutters or sags inorder to avoid smearing the toner image situated on both sides of thecarrier material 22. When the operating mode of “simplex printing”having only single-sided toner images on the carrier material 22 isapplied, contact can occur at that side of the carrier material 22 lyingopposite the toner images, and corresponding guide elements can beprovided.

Due to the friction between ambient air and carrier material 22, air isentrained in the region of a boundary layer as a consequence of thetransport motion of the carrier material 22. Upon entry of the carriermaterial 22 into the fixing chamber 40, ambient air is therefore alsotransported into the fixing chamber 40 through the admission gap 42. Asa consequence of the movement of the carrier material 22, solvent vaporis entrained from the inside of the fixing chamber 40 at the dischargeside toward the outside through the discharge gap 44. As a result ofthese effects, the solvent concentration in the inside of the fixingchamber is steadily reduced if this effect is not countered. In order todiminish this effect, first, the admission gap 42 and the discharge gap44 are implemented optimally narrow; second, fresh solvent vapor iscontinuously resupplied into the fixing chamber 40 from an evaporatorduring the fixing process.

FIG. 6 shows a preferred exemplary embodiment [of the invention] whereintoner images can be fixed on both sides of the carrier material 22, thefixing chamber comprising a solvent charging system which charges thetoner image with a solvent vapor. The fixing chamber is symmetricallyconstructed relative to the carrier material web 22. Components areexplained below that are required for the fixing of the toner imagespresent on the upper side of the carrier material web 22. An evaporator46 to which liquid solvent is supplied via a delivery tube 48 isarranged inside the fixing chamber 40. The solvent drips onto a heatedplate 50 as a healing system whose temperature lies above the boilingpoint of the solvent, for example 30° C. above the boiling point. Inorder to improve the evaporation process, the plate 50 can be chemicallyor mechanically roughened or can be provided with channels. Thegenerated vapor stream 52 escapes via an opening 54. This opening 54 canbe designed as a slot or as a nozzle. In a preferred exemplaryembodiment, the opening 54 is designed as a valve, and preferably as asolenoid valve. The escape of the vapor stream 52 can be controlled bydesign, with a clocked opening and closing of the valve.

Alternatively, the delivery of the solvent can also ensue with a nozzle.This nozzle (not shown) generates a finely atomized jet of solvent thatis sprayed onto the heated plate 50.

The vapor stream 52 escaping from the evaporator 46 is supplied to thesuction side of a cross current ventilator 56 as an acceleration devicethat is designed as a radial ventilator. The speed of the cross currentventilator 56 can be regulated in order to set the flow velocity of thestream 34 composed of a mixture of air and solvent vapor. With theassistance of the gap nozzle 36, the stream 34 is directed onto thecarrier material 22 obliquely in the transport direction P1 of thecarrier material 22. The directed stream 34 is then guided along achannel 58 along the carrier material 22 and is extracted by the crosscurrent ventilator 56 at the end of the channel 58 in order to becompressed to form a directed stream 34 mixed anew with the fresh vaporstream 52. The flow velocity of the stream 34 generally amounts to amultiple of the transport velocity of the carrier material 22. In thisway, the same part of the stream 34 with the solvent vapor canrepeatedly act on the toner images on the carrier material 22 within aninfluencing time that is defined by the length of the channel 58 and bythe transport velocity.

The solvent vapor responsible for the dissolving of the toner materialis supplied to the toner material in the toner images in a circulationupon continuous circulation of the solvent vapor. The continuouscirculation of the solvent produces a homogenization of the solventconcentration within this circulation and, thus, a homogenization of thefixing of the toner images on the carrier material 22. Blowing adirected stream 34 against the carrier material 22 accelerates thefixing event, so that a lower solvent concentration suffices for thefixing, or solvents having reduced dissolving power can be employed.

According to the exemplary embodiment according to FIG. 6, the gapnozzle 36 generates a stream 34 that obliquely impinges the carriermaterial 22. Due to the oblique positioning of the gap nozzle 36, anunder-pressure or, respectively, a constant pressure is produced in theregion of the admission gap 42. The entry of air due to the transportmotion of the carrier material 22 can thus be minimized by means of askillful selection of the angle of incidence of the gap nozzle 36.

In the example of FIG. 6, components of the directed stream 34 and ofthe transport direction P1 are isodirectional. Such an arrangement isreferred to as a co-current flow principle. The arrangement can also bedesigned such that components of the stream 34 and of the transportdirection P1 are opposite one another. This arrangement is referred toas a counter-current principle.

When the carrier material 26 carries toner images on only one side, forexample the upper side, then the component parts for fixing toner imagesof the lower side can be foregone, i.e. the component parts such as theevaporator, the cross current ventilator, etc., that are arranged underthe carrier material in FIG. 6.

The arrangement according to FIG. 6 can be designed such thatcombustible solvents that require device-oriented safety measures in theframework of explosion protection can be utilized. An explosion flap 60that opens given increased pressure is thus arranged in the region ofthe discharge gap 44. The carrier material 22 is electrostaticallydischarged by means of ionized air with the assistance of a dischargedevice 62. All ignition sources within the fixing chamber 40 areavoided. All parts of the apparatus are grounded in order to avoidstatic charging. A respective extraction device 64, 66 that extracts thesolvent vapor escaping from the fixing chamber 40 in slight amounts isarranged in the proximity of the admission gap 42 and of the dischargegap 44. Accordingly, no concentrations of solvent vapors that areexplosive or harmful to health can occur outside of the fixing chamber,even given longer operation.

The arrangement according to FIG. 6 is also designed for a faststart/stop behavior. Two control flaps 70, 72 are provided for thispurpose, these being shown in the enable position in FIG. 6. In thisposition, the stream 34 can flow freely. Both control flaps 70, 72 canbe swiveled into a deflection position according to the swivelingdirections P2, P4, so that the carrier material 22 no longer has solventvapor blown against it. For immediate interruption of the fixingprocess, the control flaps 70, 72 are moved into the deflectionposition. At the same time, the delivery of solvent via the deliverypipe 48 is stopped for the evaporation process, and the extractiondevice 66 is turned off. The other extraction device 64 then suctionsfresh air into the fixing chamber 40 and the channel 58, and thus theregion around the carrier material 22 is flooded with fresh air. Thefixing process is suddenly interrupted by means of these measures.

Upon resumption of the printing operations and the further transport ofthe carrier material 22, the fixing process is restarted by swivelingthe control flaps 70, 72 opposite the directions P2, P4. At the sametime, the extraction device 66 is re-activated and the admission ofsolvent for the evaporator 46 is started.

In certain printing processes, the carrier material 22 is retracted inthe direction of the printing unit opposite the direction P1 before theresumption of the printing operations. In this case, the control flaps70, 72 are not returned into the enable position until unfixed tonerimages are again situated in the blowing location in the channel 58.What is thus achieved is that toner images that have already been fixedneed not undergo the fixing process again.

A sensor that measures the solvent concentration is connected into thecirculation with solvent vapor. As shall be explained in greater detaillater, the solvent concentration is regulated to a constant value withthe assistance of this sensor 74.

In the delivery of solvent into the circulation for solvent vapor and inthe guidance of the solvent vapor in the circulation, care must beexercised to see that no larger drops of solvent that could fall ontothe carrier material 22 form anywhere due to condensation. For thisreason, all walls in the fixing chamber that come into contact with thesolvent vapor are heated. The temperature of these walls is set suchthat it at least has the temperature of ebullition of the solvent orlies above this.

FIG. 7 shows an example of a fixing mechanism similar to FIG. 6.However, the counter-current principle is realized here, i.e. the stream34 with solvent vapor is directed opposite the transport direction P1 ofthe carrier material 22.

FIG. 8 shows another version of the invention. In this version, theexpansion of the evaporating solvent is utilized in order to generate adirected stream 34 that contains solvent vapor. Liquid solvent issupplied to the evaporator 46 via the delivery pipe 48. The nozzle 36generates the directed stream 34 that blows against the carrier material22. The flow velocity and the volume stream are dependent on thequantity of solvent evaporated. A gap nozzle is also preferably employedhere as nozzle 36. However, it is also possible—and this is also true ofthe other example—to have the solvent vapor flow out from a plurality ofsmall round nozzles that are attached over the width of the carriermaterial 22. In the example of FIG. 8, the carrier material 22 does nothave a vapor stream circulation blowing multiply against it.

FIG. 9 shows a further version of a fixing device of the inventionwherein a directed stream 34 is generated on the basis of the expansionduring the evaporation of the solvent. This stream 34 is directed ontothe carrier material 22 only once. The version according to FIG. 9 issuited for low transport speeds of the carrier material 22.

FIG. 10 shows a further version wherein the evaporator 46 is arrangedoutside the fixing chamber 40. The opening 52 is gap-shaped and islocated in the proximity of the cross current ventilator 56 at thesuction side thereof. The opening 54, however, can also have otherembodiments. Expressed in general terms, the introduction point for thefresh vapor into the circulation can be situated at an arbitrary pointof the circulation.

FIG. 11 shows an exemplary embodiment for simplex printing. The fixingprocess with the directed stream 34 only takes effect on one side of thecarrier material 34. The co-current flow principle is applied in theexample according to FIG. 11, whereby the stream 34 proceeds in thedirection P1 of the transport of the carrier material 22.

FIG. 12 shows the example of FIG. 11 with a counter-current principle,whereby the stream 34 proceeds opposite the transport direction P1.

FIG. 13 shows an example wherein two circulations with streams 34 a and34 b are successively generated. Both stream 34 a, 34 b act on the sameside of the carrier material 22. The streams 34 a and 34 b are generatedin two series-connected fixing chambers 40 a, 40 b. The synchronousprinciple is applied in both chambers chamber 40 a, 40 b.

FIG. 14 shows an example similar to FIG. 13. The co-current flowprinciple is applied in the chamber 40 a and the counter-currentprinciple is applied in the chamber 40 b.

FIG. 15 shows another example similar to that of FIG. 14, whereby,however, the streams 34 a and 34 b are generated in a single fixingchamber 40. The combined co-current/counter-current principle accordingto the example of FIG. 14 is retained.

FIG. 16 shows an embodiment wherein the carrier material 22 isvertically conducted through the fixing chamber 40. As a consequence ofthe forced flow, the fixing process—expressed in general terms—isindependent of the transport direction of the carrier material. Greaterdegrees of freedom thus derive in the design and the incorporation ofthe fixing device in a printer or copier.

FIG. 17 shows an example wherein the carrier material 22 is conductedthrough the fixing chamber 40 at an angle of approximately 400.

FIG. 18 shows the exemplary embodiment according to FIG. 6, whereby thecontrol flaps 70 and 72 are swiveled into the deflection position. Thestream 34 is deflected with the assistance of these control flaps 70, 72such that it no longer blows against the carrier material 22. At thesame time, the delivery of solvent into the evaporator 46 is stopped andthe extraction device 66 is turned off. The extraction device 64 thatcontinues to operate then suctions fresh air into the fixing chamber 40,as a result whereof the carrier material 22 is flooded with fresh air.The fixing process is instantly interrupted by means of these measures.For resuming the fixing operations, the control flaps 40, 72 areswiveled back into a position as entered in FIG. 6. At the same time,the extraction device 66 is activated and the solvent delivery into theevaporator 46 is started.

FIG. 19 shows the fixing device according to FIG. 6 with further controlelements. As a result of the steady dragging of air into the fixingchamber 40 that cannot be completely prevented due to the movement ofthe carrier material 22, solvent must be constantly replenished duringthe fixing operations in order to maintain the solvent concentration.The sensors 74 a and 74 b serve for detecting the solvent concentration,these sensors acquiring the concentration above the carrier material 22on the one hand and under the carrier material 22 on the other hand. Thesignals of the sensors 74 a, 74 b proceed to regulators 80 a, 80 b thatact on solenoid valves 76 a, 76 b that are connected into the admissionlines 82 a, 82 b for the solvent. In the open condition of the solenoidvalves 76 a, 76 b, solvent proceeds from a reservoir 78 to theevaporator chamber 46 a, 46 b. The regulators 80 a, 80 b set the openingtimes of the solenoid valves 76 a, 76 b such that the solventconcentration in the stream 34 a or 34 b has a constant value.

The advantages of the fixing device of the invention shall be summarizedagain on the basis of the described exemplary embodiments. Theillustrated fixing devices make it possible to fix toner images on thecarrier material contact-free. The toner image as well as the carrier,for example sensitive paper, are not damaged and no pressure points andno stripping or crushing of the toner arise. Further, wear parts asrequired, for example, in the form of the fixing drums givenheat-pressure fixing, are eliminated.

The fixing device enables an intermittent operation since a faststart/stop mode can be realized. The structural size of the fixingdevice is relatively small compared to traditional fixing devices andcomparable transport speeds, for example transport speeds above 1 m/s.Due to the circulation of the solvent vapor and of the directed stream,a very homogeneous fixing image is achieved.

The fixing process is improved by blowing the carrier material withsolvent vapor and, in particular, due to the circulation principle, sothat less solvent given reduced consumption is required. Anenvironmentally safe solvent with reduced dissolving power can likewisebe employed, whereby the transport speed can be high, i.e. above 1 n/s.The degree of softening of the toner material can be influenced by thesolvent concentration in the fixing chamber. The degree of penetrationof the toner into the paper can thus be controlled. For specificdemands, for instance increased document security, the fixing device ofthe invention makes it possible to achieve such a great penetration ofthe toner into the carrier material that this toner can only be removedfrom the carrier material with great expense or cannot be removedtherefrom at all.

Given the recited fixing process, the fixing is largely independent ofthe thickness of the carrier material; for example, thin and thickpapers can be processed. Due to the low temperature prevailing in coldfixing, a low thermal stress derives, so that heat-sensitive carriermaterials such as, for example, films and labels can be employed.

During fixing in the fixing chamber, the carrier material is onlyslightly heated, so that it is not dehumidified or hardly dehumidified.Changes in moisture are thereby avoided and disadvantageous effects suchas ripple, bagging or curling of the carrier material do not occur.Toners having different colors can be simultaneously fixed with theassistance of the described fixing devices.

The fixing device allows halogen-free solvents to be preferably employedsuch as, for example, ethyl acetate, acetone, isopropanol, n-propanol.The solvent can be single-phase, as a result of which the condensationand processing of the solvent vapors that emerge from and are extractedfrom the fixing chamber are very simple in the framework of a recovery.As a result of this recovery and re-employment of the solvent, theoverall solvent consumption can be reduced further.

Toner having an arbitrary polymer basis such as, for example, on thebasis of polystyrol, polyester and others can be utilized. There isgenerally a suitable solvent for each of these polymers.

While a preferred embodiment has been illustrated and described indetail in the drawings and foregoing description, the same is to beconsidered as illustrative and not restrictive in character, it beingunderstood that only the preferred embodiment has been shown anddescribed and that all changes and modifications that come within thespirit of the invention both now or in the future are desired to beprotected.

1. An apparatus for fixing a toner image on a carrier material,comprising: a fixing chamber having a charging system which charges thetoner image with a solvent vapor via a directed stream containing thesolvent vapor; said charging system comprising a nozzle directing thestream onto a section of the carrier material; and walls of the fixingchamber which come into contact with the solvent vapor being heated to atemperature that is at least equal to or higher than a temperature ofebullition of a liquid solvent used to form said solvent vapor.
 2. Theapparatus according to claim 1 wherein an acceleration device isprovided which generates the stream containing the solvent vapor.
 3. Theapparatus according to claim 2 wherein a cross-current ventilator isprovided as the acceleration device.
 4. The apparatus according to claim1 wherein a portion of the solvent vapor not absorbed by the carriermaterial and the toner image is enriched with a predetermined quantityof freshly evaporated solvent and recirculated back to the nozzle and aportion of the evaporated solvent which exits from the fixing chamberbeing extracted by an extraction device.
 5. The apparatus according toclaim 1 wherein the carrier material is web-shaped paper.
 6. Theapparatus according to claim 1 wherein the carrier material istransported in non-contacting fashion in a region in which it receivesthe solvent vapor.
 7. The apparatus according to claim 1 wherein thecarrier material is electrostatically discharged with assistance of adischarge device before it receives the solvent vapor.
 8. The apparatusaccording to claim 1 wherein the stream of solvent vapor is directed ina moving direction of the carrier material.
 9. The apparatus accordingto claim 1 wherein the stream of solvent vapor is directed opposite amoving direction of the carrier material.
 10. The apparatus according toclaim 1 wherein the stream of solvent vapor is guided along a channelsection having a defined length and within which the solvent vapor actson the toner image and on the carrier material.
 11. The apparatusaccording to claim 1 wherein a gap nozzle is provided as said nozzle.12. The apparatus according to claim 1 wherein a heated plate onto whichthe liquid solvent is dripped is provided for evaporation of thesolvent.
 13. The apparatus according to claim 12 wherein the solvent issupplied by a delivery pipe; and the heated plate is at least one ofroughened and provided with channels.
 14. The apparatus according toclaim 12 wherein the solvent is supplied to the heated plate withassistance of a spray nozzle that sprays the solvent.
 15. The apparatusaccording to claim 1 wherein at least one valve controls flow of thesolvent from a reservoir.
 16. The apparatus according to claim 15wherein the valve is driven such that a predetermined concentration ofsolvent is maintained in the stream of the solvent vapor.
 17. Theapparatus according to claim 15 wherein at least one sensor is providedthat measures the solvent concentration in the stream of solvent vapor;and the concentration of the solvent is regulated by control of asolenoid valve.
 18. The apparatus according to claim 1 wherein a vaporstream valve is provided that regulates delivery of the solvent vaporfrom an evaporator.
 19. The apparatus according to claim 1 wherein thefixing chamber is secured by at least one explosion flap.
 20. Theapparatus according to claim 1 wherein the carrier material is guided inthe fixing chamber via an admission gap and a discharge gap; and arespective extraction device which extracts at least a portion of thesolvent vapor is provided at the admission gap and at the discharge gap.21. The apparatus according to claim 1 wherein at least one control flapis provided with which the stream of solvent vapor is deflected in adeflection position such that the carrier material no longer has solventvapor blown against it.
 22. The apparatus according to claim 21 whereinfor immediate interruption of fixing, the control flap is driven intothe deflection position.
 23. The apparatus according to claim 1 whereingiven a stop of forward transport of the carrier material, fixing isalso stopped.
 24. The apparatus according to claim 1 wherein givenresumption of transport of the carrier material, a control flap isswiveled from a deflection position into an enable position for thestream of solvent vapor.
 25. The apparatus according to claim 1 whereinthe carrier material inside the fixing chamber is simultaneouslyrespectively charged from both sides with a respective directed streamof the solvent vapor.
 26. The apparatus according to claim 1 wherein anevaporator for generating the solvent vapor is arranged outside thefixing chamber.
 27. The apparatus according to claim 1 wherein thecarrier material as viewed in a transport direction is successivelycharged by a first stream containing the solvent vapor and then by asecond stream containing the solvent vapor.
 28. The apparatus accordingto claim 27 wherein the first stream and the second stream areidentically directed.
 29. The apparatus according to claim 27 whereinthe first stream and the second stream are directed opposite oneanother.
 30. The apparatus according to claim 27 wherein both streamsare generated in a single chamber.
 31. The apparatus according to claim27 wherein each stream is generated in a chamber.
 32. The apparatusaccording to claim 1 wherein the solvent has a low ozone potential. 33.The apparatus according to claim 1 wherein the solvent is single-phase.34. The apparatus according to claim 1 wherein one of ester, ketone, andalcohol is employed as said solvent.
 35. The apparatus according toclaim 1 wherein a toner comprising polystyrol is employed.
 36. Anapparatus for printing and/or copying, comprising: a band-shaped carriermaterial printed with toner images on at least one side; and a fixingchamber for fixing the toner image on the carrier material, said fixingchamber having a charging system which charges the toner image with asolvent vapor via a directed stream containing the solvent vapor, saidcharging system comprising a nozzle directing the stream onto a sectionof the carrier material, and walls of the fixing chamber which come intocontact with the solvent vapor being heated to a temperature that is atleast equal to or higher then a temperature of ebullition of a liquidsolvent used to form said solvent vapor.
 37. A method for fixing a tonerimage on a carrier material, comprising the steps of: charging a tonerimage with a solvent vapor by generating and directing an air streamcontaining the solvent vapor onto a section of the carrier material withthe assistance of a nozzle; and heating walls of a fixing chamber whichcome into contact with the solvent vapor to a temperature that is atleast equal to or higher then a temperature of ebullition of a liquidsolvent used to form said solvent vapor.
 38. The method according toclaim 37 wherein an acceleration device is provided for generating thestream containing the solvent vapor.
 39. The method according to claim37 wherein a portion of the solvent vapor not absorbed by the carriermaterial and the toner image is enriched with a predetermined quantityof freshly evaporated solvent and then recirculated back to the nozzle,and wherein a portion of the solvent vapor escaping from fixing thechamber containing the solvent vapor is extracted by an extractiondevice.
 40. The method according to claim 37 wherein the stream ofsolvent vapor is directed in a moving direction of the carrier material.41. The method according to claim 37 wherein the stream of solvent vaporis directed opposite a moving direction of the carrier material.
 42. Themethod according to claim 37 wherein the carrier material inside thefixing chamber is simultaneously respectively charged from both sideswith a directed stream of the solvent vapor.
 43. The method according toclaim 37 wherein the solvent vapor has a low ozone potential.
 44. Themethod according to claim 43 wherein the solvent vapor is single-phase.45. The method according to claim 37 wherein one of ester, ketone, andalcohol is employed as said solvent vapor.
 46. The method according toclaim 37 wherein a polystyrol toner is employed.
 47. A vapor fixingdevice for an electrographic printer or copier, comprising: a heatedvapor housing having vapor therein used for fixing a toner image on acarrier material, and walls of said vapor housing which come intocontact with the vapor being heated to a temperature sufficiently highso that the vapor does not condense at an interior of housing walls ofthe housing.
 48. The apparatus according to claim 47 wherein a nozzle isprovided within the vapor housing directing a stream of the vapor onto asection of the carrier material.
 49. A method for vapor fixing a tonerimage onto a carrier material, comprising the steps of: providing vaporin a vapor housing; and heating interior walls of the vapor housingwhich come into contact with the vapor to a temperature sufficientlyhigh so that vapor does not condense at the interior housing walls ofthe housing.
 50. The method according to claim 49 including the step ofdirecting a stream of a vapor against the carrier material to fix thetoner image on the carrier material.